Technology advances continue to increase the storage capacity of disk drives at a rate that is much faster than the improvements in disk drive performance. The manufacturers of disk drives continue to focus their research and development on increasing the storage capacity of a disk platter.
As a result it is common to have disks in which the storage capacity continues to double but for which the performance per unit of storage is rapidly getting worse with each generation.
In many applications this problem is addressed by designing systems with a larger number of smaller disks to increase concurrent parallel access to the data.